The prior art vibrating quartz diaphragm pressure sensor is described in U.S. Pat. No. 4,479,070, issued Oct. 23, 1984.
The prior art process of bonding crystalline quartz plates of a vibrating quartz diaphragm pressure sensor uses nonmetallic materials, such as epoxies and frits and the like.
One problem with such nonmetallic materials is that they have organic carriers, which tend to outgas into vacuum cavities in the sensor, thereby causing stability problems. Another problem with such nonmetallic materials is that they are applied in layers of relatively large thickness, thereby causing relatively high bonding stresses and warping of the plates. Still another problem with such nonmetallic materials is that they have a thermal expansion coefficient which is substantially different from the thermal expansion coefficient of the plates, thereby causing additional bonding stresses and warping of the plates.